A Dynamic Approach to the Estimation of Morbidity

Abstract

Degenerative diseases are inherent in human beings. They are caused by the aging process, and the morbidity rate in these diseases usually increases with age.

Unfortunately, the routine morbidity statistics in all countries record only some of the cases of degenerative diseases, and it is necessary to estimate the true number of cases on the basis of other indirect statistics - in particular, mortality data.

The development of the morbidity models at IIASA is directed toward reducing the restrictions on the changes in population structure and disease. For example, the assumption that population structure is stable and stationary implies that this type of model can be applied only to populations with a monotonic-like age structure. In addition, it is necessary to adapt these models to use comprehensive health study data about a specific region, in order to avoid extending clinical survival data to the latent sick individuals.

One way to overcome these difficulties is to use the state-space approach to describe disease dynamics. This approach is used in the model developed for the estimation of morbidity rates in the case of unstable and unstationary population structures (DYMOD). The application of this model has required corresponding medical and demographic statistics for several consecutive years; and data collected from the South West Region of the UK and the Netherlands were used in testing the DYMOD model.